Hybrid refrigeration system for a mobile unit and method of operation

ABSTRACT

A refrigeration system for a mobile unit and a method for operating the same are provided. The method includes the steps of: 1) providing a refrigeration unit having a compressor, an evaporator, and at least one fan operable to move air towards the evaporator, a generator dedicated to the refrigeration unit, and a battery; 2) determining at least one environmental parameter in one or both of the mobile unit and the refrigeration unit; and 3) selectively operating the refrigeration unit in one of a plurality of modes based on the environmental parameter, which plurality of modes includes a first mode wherein at least the fan is powered by the battery, and a second mode wherein the compressor and the fan are powered by the generator.

Applicant hereby claims priority benefits under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 61/255,318 filed Oct. 27, 2009,the disclosure of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

This disclosure relates generally to heat exchange systems and, moreparticularly, to a hybrid refrigeration system for a mobile unit.

2. Background Information

Heat exchange systems can be used to regulate environmental conditionswithin a mobile unit (e.g., a vehicle, a truck container, a trucktrailer, a shipping container, etc.). Typically, heat exchange systemsare powered either directly or indirectly by an internal combustionengine. The engine may be operated during high load conditions (e.g.when the heat exchange systems require/draw a relatively large quantityof power), during low load conditions (e.g. when the heat exchangesystems require a relatively small quantity of power), and during idleconditions (e.g. when the heat exchange systems are idle and require nopower).

In an effort to reduce energy consumption and costs associatedtherewith, it is known to operate the engine of a heat exchange systemin an operational mode where the engine is subject to periods ofoperation and periods of rest. This mode of operation can be referred toas a “start and stop” mode of operation. One of the issues with thestart and stop mode of operation is that when the engine is needed butthe load on the heat exchange system is low, the engine may produce morepower than the heat exchange system requires, which negatively effectsthe efficiency of the system. Another issue with the start and stop modeis that when the system is not operating, the air within the mobile unitis likely to be not circulating. As a result, localized thermal hotspots(and associated steep temperature variances) may form within the mobileunit. The formation of these hotspots can lead to inaccurate temperaturereadings and reduce the efficiency of the system. For example, if thetemperature of the air proximate a sensor within the mobile unit ishigher or lower than air elsewhere within the unit, the informationprovided by the sensor and any actions based on that information may besuspect. To reduce these inaccurate readings, some prior art systems“prime” the sensors within the mobile unit. The term “prime” is used torefer to scenarios where the prior art heat exchange system, includingthe engine, is run to circulate air within the mobile unit for a periodof time until the temperature of the air within the mobile unit is moreuniformly distributed. However, similar to low load conditions, theengine used to create the circulation typically produces more power thanis required to “prime” the system and energy is consequently wasted.There is, therefore, a need in the art for a heat exchange system thatreduces energy consumption during low load conditions.

SUMMARY OF THE DISCLOSURE

According to one aspect of the invention, a method for operating arefrigeration system for a mobile unit includes the steps of: 1)providing a refrigeration unit having a compressor, an evaporator, andat least one fan operable to move air towards the evaporator, agenerator dedicated to the refrigeration unit, and a battery; 2)determining at least one environmental parameter in one or both of themobile unit and the refrigeration unit; and 3) selectively operating therefrigeration unit in one of a plurality of modes based on theenvironmental parameter, which plurality of modes includes a first modewherein at least the fan is powered by the battery, and a second modewherein the compressor and the fan are powered by the generator.

According to another aspect of the invention, a refrigeration system fora mobile unit is provided. The refrigeration system includes arefrigeration unit, a battery and a controller. The refrigeration unitincludes a compressor, an evaporator, a generator, and at least one fanoperable to move air through the evaporator. The generator is dedicatedto the refrigeration unit. The controller is adapted to selectivelyoperate the refrigeration unit in one of a plurality of modes based onan environmental parameter within the mobile unit, which plurality ofmodes includes a first mode wherein the fan is powered by the battery,and in a second mode wherein the compressor and the fan are powered bythe generator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of one embodiment of arefrigeration system for regulating environmental conditions in a mobileunit.

FIG. 2 is a diagrammatic illustration of one embodiment of therefrigeration system in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a mobile refrigeration unit 10 operable to regulateenvironmental conditions (e.g., air temperature) in a truck trailer 12.Mobile refrigeration units 10 can also be used with box trucks, buses,shipping containers, etc. The portion of the trailer 12 or othercontainer that is to be environmentally maintained by the refrigerationunit 10 is referred to hereinafter as the “control region”.

A diagrammatic illustration of an embodiment of a refrigeration unit 10is shown in FIG. 2. The refrigeration unit 10 includes a power package14, a compressor 16, a condenser 18, a refrigerant regulator 20, anevaporator 22, at least one fan 24, and a control system 26(“controller”). The refrigeration unit 10 is configured such that liquidrefrigerant travels through the compressor 16, the condenser 18, therefrigerant regulator 20 and the evaporator 22 in a closed loop path 28.The fan 24 has an alternating current (“ac”) motor or a direct current(“dc”) motor and is configured to direct air 30 from the control region,and/or in some embodiments from outside the control region, through theevaporator 22, and back into the control region. A detailed example of arefrigeration unit is disclosed within U.S. Pat. No. 5,916,253, which ishereby incorporated by reference in its entirety.

The power package 14 includes a motor 32 coupled to a generator 34, anda battery 36. The power package 14 is adapted to power to one or more ofthe components of the refrigeration unit 10 (e.g. the compressor 16, therefrigerant regulator 20, the fan 24, the controller 26, etc.) and, insome embodiments to maintain or replenish the charge of the battery 36.An example of an acceptable motor 32 is a compact diesel engine of thetype that is commonly used to power a refrigeration unit 10. An exampleof an acceptable generator 34 is a permanent magnet type DC generator.Alternatively, an AC alternator can be included in the power package 14.The power package 14 is dedicated to the refrigeration unit 10. The term“dedicated” is used to indicate that the refrigeration unit 10 derivesall or substantially all of its power from the power package 14. Thebattery 36 is operable to provide electrical power to one or more of therefrigeration unit components (e.g., the compressor 16, refrigerantregulator 20, fan 24, controller 26, etc.). In some embodiments, thecharge of the battery 36 is maintained or replenished using powerreceived from the generator 34. Systems for maintaining or replenishingthe charge of a battery 36 are well known in the art and furtherdescription is not required here for enablement purposes. The battery 36may be a single unit or multiple units combined.

The controller 26 includes a processor 38 that is adapted to receive oneor more feedback signals from one or more sensors 40, positioned withinthe control region and/or the refrigeration unit 10, indicative of anenvironmental parameter (e.g., temperature, pressure, humidity, etc.)within the control region, and/or feedback signals indicative ofoperating parameters of the refrigeration unit 10. The processor 38 isfurther adapted to selectively maintain or change the operating mode ofthe refrigeration unit 10, using actuators 42 (e.g., switches, valves,etc.) in communication with the refrigeration unit 10 based on thefeedback signals, an algorithm, or some combination thereof. Forexample, a temperature value sensed within the control region may promptthe controller 26 to engage a non-operating refrigeration unit 10 tosupply cooling air to the control region, or it may prompt thecontroller 26 to disengage an operating refrigeration unit 10.Similarly, an operating parameter value associated with therefrigeration unit 10 may prompt the controller 26 to engage a dormantrefrigeration unit 10, or to disengage an operating refrigeration unit10. It should be noted that the functionality of the processor 38 may beimplemented using hardware, software, firmware, or a combinationthereof. A person skilled in the art would be able to program theprocessing unit to perform the functionality described herein withoutundue experimentation.

The refrigeration unit 10 can be operated in a variety of differentmodes. In a first mode, for example, the controller 26 directs therefrigeration unit 10 to operate the fan 24 only to circulate air to andfrom the control region. The power to drive the fan 24 is provided bythe battery 36, and the motor 32 and generator 34 of the power package14 are maintained in non-operational mode. The other components of therefrigeration unit 10 (e.g., the compressor 16, etc.) are alsomaintained in non-operational mode.

In a second mode, the controller 26 directs the refrigeration unit 10 tooperate the fan 24 to circulate air to and from the control region, andto operate at least one of the other components (e.g., the compressor16, etc.) of the refrigeration unit 10. The power to drive the fan 24and the other component is provided by the battery 36, and not by themotor 32 and generator 34 of the power package 14.

In a third mode, the controller 26 directs the refrigeration unit 10 tooperate the fan 24 to circulate air to and from the control region, andoperate at least one of the other components (e.g., the compressor 16,etc.) of the refrigeration unit 10. The power to drive the fan 24 andthe other component is provided by motor 32 and generator 34 of thepower package 14.

The above described modes of operation are examples of how the presentrefrigeration unit 10 may be operated, and the present refrigerationunit 10 should not be construed as being limited to these particularmodes. Additional information regarding circumstances when these modesmay be implemented is provided below.

In operation of the present refrigeration unit 10, the controller 26receives the feedback signal(s) indicative of the environmentalparameter(s) in the control region and/or the operational parameter(s)of the refrigeration unit 10. If, for example, the feedback signalsindicate that the refrigeration unit 10 should be operating in a lowload condition (e.g., temperature sensed within the control region isequal to or below the desired temperature for a cooling application),the controller 26 may operate the refrigeration unit 10 according to thefirst mode, wherein the battery 36 is used to power the fan 24 alone tocirculate air to and from the control region. In some applications, thecontroller 26 may dictate a variable air flow rate created by the fan 24based on feedback signals.

While operating in the first mode, the circulation of the air may reduceor prevent the formation of regional thermal hotspots within the controlregion. The speed and extent to which the air circulation will eliminatethe regional hotspots will depend upon factors including the volumetricflowrate of the fan 24, the configuration of objects within the controlregion, the size of the control region, etc. Once an effective flow rateof air is circulated, the sensors 40 are apt to determine temperaturevalues that are more representative of the average temperature withinthe control region, as opposed to a disparate regional temperaturevalues. Consequently, it may be possible to reduce or eliminateassociated sensor priming periods. In the first mode, the refrigerationunit 10 can be operated for a period of time without running the motor32 and generator 34 of the power package 14. Consequently, whatever fuelwould have been consumed by the motor 32 is saved. What constitutes a“low load” condition can be determined for the particular applicationand the controller 26 can be appropriately adapted.

If the feedback signals are indicative of a medium load condition (e.g.,when the temperature sensed in the control region is within apredetermined temperature range), the controller 26 may operate therefrigeration unit 10 according to the second mode, wherein the battery36 is used to power the fan 24 and one or more of the other componentsof the refrigeration unit 10. In the second mode, the fan 24 and one ormore other components of the refrigeration unit (e.g. the compressor 16,etc.) are operated for a period of time without engaging the motor 32.Hence, whatever fuel would have been consumed by the motor 32 is saved.What constitutes a “medium load” condition can be determined for theparticular application and the controller 26 can be appropriatelyadapted.

If the feedback signals are indicative of a high load condition (e.g.,the sensed environmental temperature in the control region above thefirst predetermined range of temperatures), the controller 26 mayoperate the refrigeration unit 10 according to the third mode, whereinthe motor 32 is operated to power the entire refrigeration unit 10. Inthe third mode, the charge of the battery 36 can be replenished. Whatconstitutes a “high load” condition can be determined for the particularapplication and the controller 26 can be appropriately adapted.

The controller 26 can also be adapted to sense the level of chargewithin the battery 36. If the charge within the battery 36 drops below apredetermined value, the refrigeration unit 10 can be operated withinthe third mode until the battery 36 is charged.

While various embodiments of the present invention have been disclosed,it will be apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the present invention is not to be restrictedexcept in light of the attached claims and their equivalents.

1. A method for operating a refrigeration system for a mobile unit,comprising: providing a refrigeration unit having a compressor, anevaporator, and at least one fan operable to move air towards theevaporator, a generator dedicated to the refrigeration unit, and abattery; determining at least one environmental parameter in one or bothof the mobile unit and the refrigeration unit; and selectively operatingthe refrigeration unit in one of a plurality of modes based on theenvironmental parameter, which plurality of modes includes a first modewherein at least the fan is powered by the battery, and a second modewherein the compressor and the fan are powered by the generator.
 2. Themethod of claim 1, wherein in the first mode the generator and thecompressor are non-operational.
 3. The method of claim 1, wherein in thesecond mode the generator charges the battery.
 4. The method of claim 1,wherein the environmental parameter is indicative of a temperaturewithin the mobile unit.
 5. The method of claim 4, further comprising thestep of providing at least one sensor disposed within the mobile unit todetermine the at least one environmental parameter.
 6. The method ofclaim 1, wherein the mobile unit is one of a truck trailer, a box truck,a bus, and a shipping container.
 7. The method of claim 2, where thefirst mode is indicative of a low load condition.
 8. The method of claim2, wherein the second mode is indicative of a high load condition. 9.The method of claim 1, wherein in the first mode the fan and thecompressor are powered by the battery.
 10. A refrigeration system for amobile unit, comprising: a refrigeration unit including a compressor, anevaporator, a generator, and at least one fan operable to move airtowards the evaporator, wherein the generator is dedicated to therefrigeration unit; a battery; and a controller adapted to selectivelyoperate the refrigeration unit in one of a plurality of modes based onan environmental parameter within the mobile unit, which plurality ofmodes includes a first mode where the fan is powered by the battery, andin a second mode wherein the compressor and the fan are powered by thegenerator.
 11. The system of claim 10, wherein in the first mode thegenerator and the compressor are non-operational.
 12. The system ofclaim 10, further comprising at least one sensor adapted to determinethe environmental parameter within the mobile unit.
 13. The system ofclaim 12, wherein the sensor is disposed within the refrigeration unit.14. The system of claim 10, wherein the dedicated generator isconfigured to charge the battery during the second mode.
 15. The systemof claim 10, wherein the mobile unit is one of a truck trailer, a boxtruck, a bus, and a shipping container.
 16. The system of claim 10,wherein in the first mode the fan and the compressor are powered by thebattery.